Manuel Pellegrini has revealed that Sergio Agüero will be out for up to eight weeks with his calf injury, casting doubt on the Manchester City striker's involvement in the first leg of the last-16 Champions League tie against Barcelona.

The City manager had initially hoped that Agüero would be unavailable for little more than a month but the latest prognosis is that the Argentinian could be on the sidelines until a week before the first leg against Barcelona at the Etihad on 18 February, leaving him desperately short of match fitness.

"I am not a doctor so it's very difficult," Pellegrini said when asked for an update on Agüero. "The doctor has said that he has at least one month or eight weeks [out]. We'll see. I don't know how many weeks but it will be at least one month."

In another injury blow, Pablo Zabaleta limped off with a pulled hamstring only 11 minutes into the 3-1 victory at Leicester. With Micah Richards sidelined with the same problem, City will go into the festive period short of a right-back. Pellegrini said the extent of Zabaleta's injury should be clear on Wednesday.

"Pablo has a problem with his hamstring, we'll see tomorrow how serious it is," Pellegrini said. "That was the only bad thing of this game. Of course [it is a concern given Micah is out for month]. We don't have a full-back. We will see what happened with Pablo but we will see what we have to do in that position. For sure for Saturday [against Fulham] he will not be fit."